초록
침지식 해수 순환 여과 사육 시스템에서 여과조 숙성과 넙치의 성장을 조사하였다. 생물 여과조가 숙성되는데 60일이 소요되었다. 사육 기간 중 수온은 17.5-25.1$^{\circ}C$, 염분은 30.1-33.5ppt, 용존산소는 7.25-10.49ppm, pH는 8.1-7.5를 유지하였다. 사육수는 매일 5% 범위에서 환수하였으며 사육수의 암모니아성 질소 및 아질산성 질소 농도는 각각 0.096-0.315mg/L 및 0.015-0.504mg/L이었으나, 질산성 질소는 질산화 과정이 지속되어 그 농도가 2.530mg/L에서 39.517mg/L까지 증가하였다. 사료 효율은 64.1-69.8% 이었고, 사육 밀도는 시험 종료 시 15.9kg/$m^2$이었다. 사육기간 중 Vibrio spp.는 검출되었으나 질병 발생에 의한 폐사는 없었으며 생존율은 97.1%를 나타내었다.
Bio-secure culture of olive flounder Paralichthys olivaceus in the IBK (Intensive Bioproduction Korean) recirculating system with dry pellet was tested for 6 months. The IBK system consists of 12 rearing tanks, 6 sedimentation tanks. 4-sectioned submerged biofilter chamber and channels. The size of each rearing tank was 3m in diameter and 1m in depth. The size of each biofilter chamber was $3.1\times3.3\times2.0$ m (D) and was filled with corrugated plastic plates as a biofilter medium. Total surface area of the biofilter was 3,789.7 $m^2$ Water was circulated by one of two vertical axial pump and circulating rate was about 34 times per day. A UV light sterilizer was used to treat inlet sea water with the flow rate of 4 ton/hr. All fish were treated with 150 ppm formalin 3 times with 5 day interval before stocking. It took 60 days for 'conditioning' the biofilter with the stocking density of 4.5 kg of fish $m^2$. The concentrations of ammonium-nitrogen, nitrite-nitrogen and nitrate-nitrogen in the system remained at the range of 0.096-0.315 mg/L, 0.015-0.504 mg/L, and 2.530-39.517 mg/L, respectively. Water temperature fluctuated from 17.5 to 25.1$^{\circ}C$ and salinity was from 30.1 to 33.5 ppt during rearing period. The fish grew from the average weight of 615.2 g to 1,201.1 g for 180 days. Initial and final fish densities were 8.4 and 15.9$kg/m^2$, Survival rate was 97.1 %. Neither parasites nor noticeable diseases was observed during the raring period even Vibrio spp. were detected from some fish in the system.
